Lazy Japanese Sea Worms: Sending Their Butts on a Mate Hunt
Some marine worms, like the Japanese green syllids, have a unique reproduction strategy where they grow a second worm on their rear ends, which then breaks off and swims away to find a mate. This detached structure, called a stolon, develops its own brain, eyes, antennae, and sex organs. The stolon's only purpose is to spawn sperm or eggs, and it dies soon after. The mechanism by which the stolon detaches is not fully understood, but it likely breaks off when it starts to wriggle. Meanwhile, a new tail bud grows on the remaining worm, allowing it to continue foraging for food as it grows its next detachable butt.